Safety based road map navigation

ABSTRACT

The disclosed subject matter relates to an architecture that can facilitate safety-oriented navigation through a local environment that presents emergency dynamics. The architecture can facilitate monitoring of deployed sensors constituting a sensor network, even for cases in which sensor locations are not known in advance such as for rapid or random deployment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 61/202,597 filed on Mar. 16, 2009 and entitled, “ROAD MAP BASEDNAVIGATION IN SENSOR NETWORKS SYSTEM AND METHOD” for all purposes. Theentirety of this application is incorporated herein by reference.

BACKGROUND

Path planning and navigation have been studied for many years inconnection with a variety of fields of study such as, for example, inthe fields of Robotics and Computational Geometry. In these or similarcontexts, environmental conditions are presumed to be globally availableand such information is further presumed to be universally shared withall other elements. Thus, centralized computing can be conducted withnearly perfect global knowledge of the environment.

However, navigation through a wireless sensor network presents a numberof difficulties. For example, in such cases, the navigation typicallymust be performed in a distributed manner over a self-organized networkconsisting of a huge number of nodes. Thus, environmental informationtypically must be rapidly captured with respect to the distributednodes. In addition, such navigation architecture would, in many cases,be required to rapidly adapt and react to environmental variations.

Previous research has been directed toward problems relating to solvingthe minimum or maximum exposure path in a network. In particular,conventional literature largely relies on exhaustive search over theentire network, which can be too slow for many practical applications.In addition, conventional systems have also proposed the use ofheuristics to compute paths in a distributed manner. However, thesesolutions treat individual sensor nodes as adversaries rather thanutilizing them as infrastructures and thus do not provide an adequatesolution for navigation in dynamic environments.

SUMMARY

The following presents a simplified summary of the disclosed subjectmatter in order to provide a basic understanding of some aspects of thedisclosed subject matter. This summary is not an extensive overview ofthe disclosed subject matter. It is intended to neither identify key orcritical elements of the disclosed subject matter nor delineate thescope of the disclosed subject matter. Its sole purpose is to presentsome concepts of the disclosed subject matter in a simplified form as aprelude to the more detailed description that is presented later.

The subject matter disclosed herein, in one or more aspects thereof,comprises an architecture that can determine safety-oriented navigationpaths in connection with a wireless sensor network deployed in ahazardous environment. Appreciably, the hazardous environment differsfrom a static environment that can be effectively navigated by avoidingcertain predetermined locations, since hazards can be newly arisen,migrate to different locations, or dissipate entirely.

In accordance therewith and to other related ends, the architecture canemploy a monitor component that can be configured to receive a hazardsignal from at least one alarming sensor included in a sensor array,wherein the hazard signal indicates a detected presence of dangerproximal to the at least one alarming sensor. The sensor array can bedistributed in a local environment, thus, the local environment can bedefined by a detection radius of the sensor array.

In addition, the architecture can include a mapping component that canbe configured to construct a road map scaled to dimensions of the localenvironment. The road map can include a route backbone that depicts oneor more recommended paths through the local environment selected basedupon a distance from the detected presence of danger.

The following description and the annexed drawings set forth in detailcertain illustrative aspects of one or more non-limiting embodiments.These aspects are indicative, however, of but a few of the various waysin which the principles of the claimed subject matter may be employedand the claimed subject matter is intended to include all such aspectsand their equivalents. Other advantages and distinguishing features ofthe claimed subject matter will become apparent from the followingdetailed description of the various embodiments when considered inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a computer-implemented system thatcan determine safety-oriented navigation paths through an environmentsubject to emergency dynamics.

FIG. 2A depicts a block diagram of a graphic depiction of example localenvironment illustrating a sensor array dispersed throughout localenvironment.

FIG. 2B depicts a block diagram of an example road map corresponding toFIG. 2A.

FIG. 3 provides block diagram of a graphic model presented illustratingan example outline of danger regions.

FIG. 4 depicts a block diagram of a graphic depiction illustrating anexample scheme for discovering or defining boundaries for danger areas.

FIG. 5 provides block diagram of a graphic depiction illustratingboundary nodes with an upper portion associated with random IDs and alower portion associated with like IDs.

FIG. 6 depicts a block diagram of a graphic depiction illustrating inmore detail construction of the route backbone.

FIG. 7 illustrates a block diagram of a graphic depiction illustrating abasic route backbone with points outside sensor range presumed to bedangerous.

FIG. 8 is a block diagram of a graphic depiction illustrating a basicroute backbone with points outside sensor range presumed to be safe.

FIG. 9 illustrates a block diagram of a graphic depiction providing aroute backbone with direction assignments for segments of the routebackbone.

FIG. 10 depicts a block diagram of a computer-implemented system thatprovides additional features in connection with determiningsafety-oriented navigation paths through dangerous environments.

FIG. 11 illustrates a block diagram of a graphic depiction illustratingconstruction of inscribed points for identifying shortcuts over routebackbone.

FIG. 12 is a block diagram of a graphic depiction illustratingidentification and/or construction of shortcuts.

FIG. 13 depicts an exemplary flow chart of procedures that define amethod for facilitating safety-based navigational guidance through adangerous area.

FIG. 14 illustrates an exemplary flow chart of procedures that define amethod for providing addition features in connection with forfacilitating safety-based navigational guidance through a dangerousarea.

FIG. 15 depicts an exemplary flow chart of procedures defining a methodfor providing for updating and/or optimizing with respect to a road mapfor traversing a dynamic environment.

FIG. 16 illustrates a block diagram of a computer operable to execute orimplement all or portions of the disclosed architecture.

FIG. 17 illustrates a schematic block diagram of an exemplary computingenvironment.

DETAILED DESCRIPTION

One or more embodiments are now described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the various embodiments. It may be evident,however, that the claimed subject matter may be practiced without thesespecific details. In other instances, well-known structures and devicesare shown in block diagram form in order to facilitate describing thevarious embodiments.

What is disclosed herein generally relates to a road map basednavigation system and method, termed as RMB, which provides humannavigation in the distributed sensor networks without relying onlocation information. RMB can embed a distributed road map in the sensornetwork, which can operate as a public infrastructure (e.g., the sensorscan be treated as waypoints for constructing suitable courses or othernavigation) for providing guidance information for internal inquiries.Multiple individual entities can issue queries to the road map and canbe instructed with regard to recommended routes to safely avoidemergency or dangerous situations or the like. Also detailed areefficient mechanisms to update the road map system according to thevariations of dangerous areas while maintaining its accuracy andeffectiveness. The incurred network traffic cost is bounded byO(√{square root over (n)}) where n is the network size. This approach iseffective and highly scalable when the network size is large andmultiple users are simultaneously navigated.

In general, RMB comprises four stages. They are: (1) building the roadmap, (2) guiding or navigating entities through suitable paths, (3)reacting to emergency dynamics, and (4) further improving routeefficiency.

In broad terms, at the first stage, the basic framework (e.g., routebackbone) of the road map can be constructed by concatenating the medialaxis of the safe region. At the second stage, the road map framework canbe utilized as a backbone for navigating different entities inside thefield. An exit in one of the cells can be identified and a routeconnecting the exit and the internal user can be constructed. Thus, eachentity can be guided through the roads to reach the destination exit.

At the third stage, the variation of dangerous areas can be categorizedaccording to four basic types, including emerging, expanding, shrinking,and diminishing. An updating principle can then be implemented whichadditively rebuilds the road map according to the emergency dynamics andaffects only a local district, by maintaining a status in each node inthe field to record the set of the closest dangerous points to that nodeand the distance between a gateway. Each time a point is switched intoor out of a dangerous area, only those points which have correlations toit are updated, such as considering the updated node as the closestdangerous point. The fourth stage relates to construction of shortcutsas supplements to the original recommended paths to improve routeefficiency and/or traversal speed.

It should be appreciated that the embedded distributed road map systemin the sensor network can provide entities navigating routes withmaximum safety without relying on predetermined location information ofthe sensor network. Rather, the road map can be generated according tothe distribution of dangerous areas and thus characterizes the featuresof safety in the field. The navigation system can maintain the road mapas a public infrastructure, and guide different entities across thefield through the same paths that are constructed or change based uponthe behavior or existence of detected dangerous conditions. Such canmitigate the unnecessary overhead extent in conventional systems ofindividually planning routes for different users. The road map canfurther be updated in an event-driven manner when the dangerous areasvary.

Given that in conventional systems unawareness of location informationalways leads to low efficiency of the system, since additionalrequirements of frequent global information exchange and coordination toassist local decisions is necessitated. Moreover, global collaborationcan be quite expensive in terms of reaction time, which is infeasibleunder many emergency situations. Accordingly, RMB addresses these issuesin a scalable way. The road map provides for an updating scheme thatadditively rebuilds the road map system in the event of changes indangerous areas, which involves fewer global operations, mitigatesnetwork overhead, and thereby is able to accommodate more requestssimultaneously over a larger area.

As used in this application, the terms “component,” “module,” “system,”or the like can, but need not, refer to a computer-related entity,either hardware, a combination of hardware and software, software, orsoftware in execution. For example, a component might be, but is notlimited to be, a process running on a processor, a processor, an object,an executable, a thread of execution, a program, and/or a computer. Byway of illustration, both an application running on a controller and thecontroller can be a component. One or more components may reside withina process and/or thread of execution and a component may be localized onone computer and/or distributed between two or more computers.

Furthermore, the various embodiments may be implemented as a method,apparatus, or article of manufacture using standard programming and/orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. For example, computerreadable media can include but are not limited to magnetic storagedevices (e.g., hard disk, floppy disk, magnetic strips . . . ), opticaldisks (e.g., compact disk (CD), digital versatile disk (DVD) . . . ),smart cards, and flash memory devices (e.g., card, stick, key drive . .. ). Additionally it should be appreciated that a carrier wave can beemployed to carry computer-readable electronic data such as those usedin transmitting and receiving electronic mail or in accessing a networksuch as the Internet or a local area network (LAN). Of course, thoseskilled in the art will recognize many modifications may be made to thisconfiguration without departing from the scope or spirit of the claimedsubject matter.

Moreover, the word “exemplary” is used herein to mean serving as anexample, instance, or illustration. Any aspect or design describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects or designs. Rather, use of the wordexemplary is intended to present concepts in a concrete fashion. As usedin this application, the term “or” is intended to mean an inclusive “or”rather than an exclusive “or.” Therefore, unless specified otherwise, orclear from context, “X employs A or B” is intended to mean any of thenatural inclusive permutations. That is, if X employs A; X employs B; orX employs both A and B, then “X employs A or B” is satisfied under anyof the foregoing instances. In addition, the articles “a” and “an” asused in this application and the appended claims should generally beconstrued to mean “one or more” unless specified otherwise or clear fromcontext to be directed to a singular form.

As used herein, the terms “hazard” or “danger” generally refer to acondition extant in an environment that is potentially harmful ordisruptive to the safety of some entity, such as a human, in theenvironment or to an action or behavior thereof. Hazards or dangers canbe sufficiently serious to necessitate or encourage evacuation of theentity from the local environment or to a safe area therein.

Referring now to the drawings, with reference initially to FIG. 1,computer-implemented system 100 that can determine safety-orientednavigation paths through an environment subject to emergency dynamics isdepicted. Generally, system 100 can include monitor component 102 thatcan be configured to receive hazard signal 104. Accordingly, monitorcomponent 102 can be equipped with a receiver, transceiver or othersuitable hardware capable of receiving an electronic signal. Asdepicted, hazard signal can be received from one or more alarmingsensor(s) 106 included in a sensor array 120. Sensor array 120(including alarming sensor 106) can be distributed throughout localenvironment 112 such that local the boundaries of local environment 112can be defined by a detection radius of sensor array 120. Moreover,hazard signal 104 can indicate a detected presence of danger 124 (e.g.,danger that is detected by at least one sensor of sensor array 120)proximal to alarming sensor 106.

As used herein, sensor array 120 as well as other references to multiplesensors are intended to refer to a sensor network in which all or aportion of the sensors in the sensor network are equipped forcommunication with one another, typically in a wireless manner.Typically, a sensor network comprises numerous sensors that can bespatially deployed in the field under surveillance, monitoring physicalor environmental conditions, such as temperature, light, radiation,vibration, composition, sound and so on. Sensors can be randomlydeployed in disaster areas or inaccessible terrain, which can enable thesensor network a wide variety of applications. Sensor networks can bespecifically adapted to many applications, including, e.g., environmentand habitat monitoring, battlefield surveillance, healthcare, trafficcontrol or the like.

In more detail, a sensor can be a device that measures a physicalquantity and converts it into signals which can be received and/orinterpreted by suitable instruments or other sensors. Sensors canconsist of a sensing unit, a processing unit, a transceiver unit, apower unit, usually a battery, as well as other suitable components,either hardware or software. The envisaged size of a single sensor nodecan vary from shoebox-sized nodes down to devices the size of grain ofdust. Sensor nodes can communicate with one other within theircommunication range, classically through radio transmission,cooperatively forming the sensor network to perform a specific sensingtask.

Most existing applications treat the sensor network as a media of dataacquisition, concentrating on organizing a data-centric network forefficiently collecting, routing, and processing in-network sensory data.Recently, however, researchers have explored more versatile applicationsof sensor networks beyond simply viewing them as tools for monitoringthe physical world. For example, in a field deployed with sensorscapable of detecting disruptive or dangerous events like a chemicalspill or outbreak of fire, the sensor network can be employed to aidnavigation, thereby guiding the movements of evacuees out of danger,which is further detailed herein.

Accordingly, the disclosed subject matter particularly relates in partto utilizing a sensor network as a reactive architecture, which canfacilitate guidance to locations of safety and/or away from danger. Inother words, a sensor network, in the presence of hazards, focus onin-situ entity interactions with the sensor network infrastructure.Moreover, in general, it is not necessary to employ one or more sinks asdata processing centers, yet there need not further be any need forcollecting and/or analyzing in the aggregate all the sensory datadistributed over the field. Rather, all operations can be carried out ina distributed manner between various entities (e.g., 160, 162) and thesensor network. For example, individual entities can be provided theability to issue queries and follow the recommended routes to safelyavoid emergency or dangerous situations.

To further underscore distinctions between the subject matter disclosedherein and conventional systems, it should be appreciated that existingapproaches require location information associated with each sensor. Incontrast, the disclosed subject matter can provide navigation withoutany pre-knowledge of either entity location or sensor location. Itshould be appreciated that in many realistic situation, where emergencyconditions exist and emergency guidance is sought, an expectation ofpre-known positions of the sensors is often unrealistic. By removingthis constraint, sensors can be randomly deployed in a rapid manner,with very little warning and without significant preparation of theenvironment beforehand. Thus, the applicability of the disclosed subjectmatter can be greatly extended.

Furthermore, the disclosed subject matter can operate in light ofemergency dynamics, which has not yet been explored by previousapproaches. Moreover, an efficient updating scheme that can locallyupdate the navigation routes when danger zones vary or migrate, whichcan substantially reduce network overhead and provide substantialscalability. Under realistic models, it is necessary to expectconditions in dangerous areas to be changing (e.g., emergency dynamics)in unpredictable and potentially rapid ways. Such variations will oftendegrade the effectiveness or even overwhelm existing designs that do notspecifically consider the impact of variations of, e.g., dangerousareas. Accordingly, the disclosed subject matter can provide timely andefficient re-planning and updating of safe routes for the users in theevent of variations with respect to dangerous areas.

Continuing the discussion of FIG. 1, system 100 can further includemapping component 110 that can be configured to construct road map 114scaled to dimensions of local environment 112. As discussed, due to theinherent scalability, local environment 112 can be virtually any size,in this case, limited only by the dimensions and detection radius ofsensor array 120. Road map 114 can include route backbone 132 thatdepicts one or more recommended paths 130 through local environment 112,which can be selected based upon a distance from detected presence ofdanger 124.

Given that road map 114 is intended to be a model or representation oflocal environment 112, there exist numerous relationships betweenelements physically extent in local environment 112 and modeled orvirtualized elements included in road map 114 such as a relationshipbetween the physical recommended path 130 that traverses localenvironment 112 and its modeled counterpart, route backbone 132 includedin road map 114. For the remainder of this document, care is taken todistinguish between related elements, however, it should be appreciatedthat where there is little chance for confusion or ambiguity to arise,corresponding terms (such as those listed in boxes 112 and 114respectively) might be utilized interchangeably. For example, whilealarming sensor 106 refers specifically to an element of localenvironment 112, it should not cause confusion for the terms “alarmingnode” (e.g., alarming node 116, which is a corresponding representationof alarming sensor 106 constructed in road map 114) to be employed inconnection with local environment 112.

Moreover, several of the terms and/or reference numerals listed in boxes112 and 114 will be introduced or further detailed with reference to theremaining figures which are intended to be referred to in conjunctionwith FIG. 1.

Hence, while still referring to FIG. 1, but turning now also to FIG. 2A,graphic depiction 200 of example local environment 112 is provided.Graphic depiction 200 illustrates sensor array 120 dispersed throughoutlocal environment. Here, as is likely to be typical, a majority of thesensors are nominal sensors 108 (depicted as white circles), for whichno presence of danger 124 or other alarming condition is detected.Additionally, a number of the sensors are alarming sensors 106 that havedetected a presence of danger 124. By combining detected presences ofdanger for all alarming sensors 106, we see three distinct danger areas140 ₁-140 ₃. Also depicted are an example recommended path 130 that canbe constructed based upon an identification of sensors in the sensorarray that are a certain minimum distance from one or more danger areas140. Furthermore, safe area 150, mobility entity 160 and gateway sensor170 also reside in local environment 112. Once these elements areconnected to recommended path 130, instructions for a safe evacuation ofmobile entity can be provided. As an example, graphic depiction 200 canrepresent an individual (e.g., mobile entity 160) who located in aforest, with the danger regions 140 indicated detected presence of afire.

Similarly, with reference to FIG. 2B, an example road map 114corresponding to FIG. 2A is illustrated. Since road map 114 is intendedto represent a model of local environment 112, the example road map 114includes corresponding elements, such as route backbone 132, dangerregions 142 (corresponding to the danger areas 140 of local environment112), exit point 152, evacuating entity 162 and gateway node 172.

While still referencing FIGS. 2A and 2B, and continuing the discussionof FIG. 1, it should be appreciated that in one or more aspect, routebackbone 132 can comprises a set of edges that join a sequence ofadjacent nodes that correspond to respective locations within localenvironment 112 of nominal sensors 108 included in the sensor array.Accordingly, mapping component 110 can identify at least one safe area150 within local environment 112 and can plot exit point 152 on road map114, wherein exit point 152 can correspond to the at least one safe area150.

Moreover, mapping component 110 can also identify at least one mobileentity 160 extant in the local environment 112 and can plot at least oneevacuating entity 162 on the road map connected to a proximal point ofroute backbone 132. Furthermore, mapping component 110 can connect theat least one exit point 152 to the route backbone 132 with an edge that(1) intersects a proximal point, denoted a gateway (e.g., 170, 172), onthe route backbone and (2) depicts recommended path 130 through localenvironment 112.

It should be understood that in one or more aspect, mapping component110 can connect the at least one exit point 152 to gateway 172 of routebackbone based upon a concatenation of a medial axis of exit point 152,wherein the medial axis can include a set of points, each of which is aminimum distance from at least two danger regions 142. These dangerregions 142 can be readily detected since mapping component 110 caninclude in road map 114 at least one danger region 142 that correspondsto danger area(s) 140 a in the local environment 114 that encompasses acontiguous set of alarming sensors 106. Moreover, when consideringregions beyond the scope of local environment 112, which can relate tohow the borders of local environment 112 are treated, various optionsexist. For example, in one aspect mapping component 110 can treatregions beyond the local environment 112 that correspond to areasoutside the detection radius of sensor array 120 as one or more of theat least one danger region 142. Additionally or alternatively, mappingcomponent 110 can treat at least one region beyond the local environment112 that corresponds to areas outside the detection radius of sensorarray 120 as a safe region 150, thus plotting an exit point 152 on roadmap 114 to correspond to the safe region 150.

In accordance with the above, one can consider the scenario of sensornetwork navigation on the field under emergencies, where there might beseveral dangerous areas that threaten the safety of human beings orother mobile entities. As discussed, a wireless sensor network can bedeployed on the field, and each entity can be equipped with acommunicating device like 802.15.4 compatible Personal Digital Assistant(PDA) that can interface with the sensors. By measuring the strength anddirection of wireless signals, the entity is able to track any targetedsensor node without fore knowledge of the location of the sensor. Anobjective of a successful navigation is to plan a path for the user toone or more pre-known exits on the field which lead to safe departure,bypassing all dangerous areas. Thus, the recommended route can berepresented by a sequence of sensor nodes and the entity can be directedalong those sensor nodes.

Referring now to FIG. 3, graphic model 300 is presented illustrating anexample outline of danger regions 142. As noted supra, given that aninitial stage is to build the road map, RMB can treat any targeted areaor curve as a set of points and each point can correspond to a sensornode. Therefore, let the entire emergent field be region E. Further, letn be the number of dangerous areas and the i-th dangerous area isD_(i)={d|d is the alarming sensor node which detects the dangerousevent}, i=1 . . . n. The combination of dangerous areas is region

$D = {\overset{n}{\bigcup\limits_{i = 1}}D_{i}}$and the remained safe region is R=E\D, as shown in FIG. 3. Accordingly,the road map is built in region R, since entities are presumed to onlymove outside dangerous areas for ensuring safety.

To provide more detail relating to construction of route backbone 132,consider that each sensor node can maintain a list of status informations, a non-limiting example of which is shown in Table I below.

TABLE I variable type Size (bits) s.danger danger ID 8 s.border Y/N 8s.mDist hops 8 s.mSet node IDs 80 s.road Y/N 8 s.nextHop node ID 8s.rDist hops 8 s.potential Value 8

In further detail, s.danger marks whether the current node resideswithin or outside a dangerous area. In this example, s.danger is 0 ifthe current node is outside the dangerous area and s.danger is set tothe ID of the dangerous area if the current node resides in such adangerous area. Appreciably, s.border can be a Boolean variable thatindicates whether the current node is on the boundary of the dangerousarea. Moreover, s.mDist records the distance (hops) from the currentnode to the nearest dangerous area, and s.mSet records the set of nodeson the boundaries of dangerous areas that are of s.mDist to the currentnode. s.road is a Boolean variable that indicates whether the currentnode is on the road map backbone. s.nextHop stores the ID of the nexthop node along the path direction on the road. s.rDist records theminimum distance (hops) to the dangerous areas on the path from thecurrent node to the exit. s.potential records the potential value of theordinary nodes

For each dangerous area, every node inside the dangerous area cangenerate a random number as s.danger and flood that number across thedanger area. The smallest number can be selected as the ID of theassociated dangerous area, which is further detailed with reference toFIG. 4.

Turning now to FIG. 4, graphic depiction 400 illustrates an examplescheme for discovering or defining boundaries for danger areas. Basedupon the foregoing alarming node 402 has generated the smallest randomnumber, 1. Thus, each node can set the s.danger to this value. For theexample in the upper portion of FIG. 4, the smallest number of thedangerous area is 1. Accordingly, every node inside that area shouldupdate each s.danger to 1, which is illustrated in the lower portion ofFIG. 4. Furthermore, nodes beyond the confines of the dangerous areasset s.danger to 0, since these nodes are nominal and/or not in analarming state, which is depicted in connection with FIG. 5.

FIG. 5 provides graphic depiction 500 illustrating boundary nodes, againwith an upper portion associated with random IDs and a lower portionassociated with like IDs. With alarming nodes all set to 1, and nominalnodes set to 0, it is readily apparent that pairs of neighboring sensorswith different outcomes will represent boundary nodes 502 when instantnode is an alarming node 106. In other words s.border can be set for thenodes within a dangerous area that detect a comparison inequality fors.danger, signifying these nodes are boundary nodes. In the lowerportion of FIG. 5, this example depicts a total of 7 boundary nodes thatare grey-filled, two of which are labeled with reference numeral 502.

Referring now to FIG. 6, graphic depiction 600 illustrating in moredetail construction of the route backbone is provided. In particular,graphic depiction 600 illustrated a set of nominal nodes (white circles)and a set of alarming nodes that are further distinguished as eitherstandard alarming nodes 106 (black fill) or boundary nodes 502 (greyfill). The set of alarming nodes are further presented in two distinctdanger regions 142, distinguished in this case by subscripts.

Boundaries nodes 502 for danger regions 142 can flood the statusinformation to the rest of the field. Accordingly, each node can recordthe distance to the nearest boundary node 502 in s.mDist and the set ofnodes on the borders of dangerous areas that are s.mDist away in s.mSet.The node whose s.mSet contains boundary nodes on two or more dangerousareas can set s.road to Y, signifying that at least one portion of routebackbone 132 will intersect the node. For example in graphic depiction600 illustrates node A is 2-hops away from both the nearest boundarynodes 502, B and C, and therefore records s.mDist=2 and s.mSet={B, C}.Since B and C are from different dangerous areas, A sets s.road=Y.

Furthermore, let the medial axis Z={z|z is the sensor node withs.road=Y}. The basic framework (e.g., route backbone 132) of the roadmap 114 can be constructed by concatenating the medial axis of region Ras illustrated. Thus, in one or more aspect of the disclosed subjectmatter, mapping component 110 can assign a potential value to a nodeincluded in road map 114 based at least in part upon data received froma corresponding sensor, wherein the potential value is inverselyproportional to a distance between the corresponding sensor and anearest danger area 140 (or danger region 142). Accordingly, mappingcomponent 110 can maximize a minimum distance from all or a portion ofdanger regions included in road map 114 to construct route backbone 132and, further can assign a direction to one or more segment of the routebackbone 132 based upon descending potential values for nodes includedin the one or more segment, which is further discussed in connectionwith FIG. 7-9.

In addition, mapping component 110 can connect exit point 152 or anevacuation entity 162 to the route backbone 132 based upon descendingpotential values for connected nodes extending from the exit point 152or the evacuation entity 162 to the route backbone 132. Appreciably, thepotential value of the node can be determined based at least in partupon information that propagates from a gateway sensor 170 thatcorresponds to a gateway node 172 for the road map 114.

In more detail, the information can propagate from the gateway sensor170 to other sensors in the sensor array 120 that correspond to nodesincluded in the road map 114, wherein the information includes, e.g.,(1) an indication of distance to a nearest danger area 140, denotedd_(c), (2) an indication of a distance to the gateway sensor 170 thatincreases as the information propagates to subsequent other sensors,denoted d_(r), and (3) a direction for the route backbone 132 for nodesalong the route backbone 132, denoted D. Accordingly, mapping component110 can construct route backbone 132 based upon a comparison betweenmultiple nodes included in the road map 114, wherein the comparisonselects nodes associated with a larger d_(c), or a smaller d_(r) whend_(c) are equal for compared nodes.

Referring now to FIGS. 7 and 8 respectively depict two examples of basicroute backbones that navigate dangerous regions. The road map frameworkcan divide a region, R, into different components, called cells, whichare denoted C₁, C₂ . . . C_(n). Each cell contains a dangerous areainside it. With the potential value s.potential=1/s.mDist, the ordinarynodes around the dangerous area in the cell comprise a virtual powerfield. In practical usage, however, when sensor nodes are sparselydeployed over the field, the nodes on the road backbone may not beconnected into one component. To solve this difficulty, we compromisethe accuracy of the medial axis, letting s.mSet of each node store theboundary nodes of both s.mDist and s.mDist+1 distance to it. By suchmeans, the medial axis is indeed broadened and more nodes are dedicatedon the road backbone, largely increasing the connectivity of routebackbone 132.

RMB will typically default to treating the area out of the sensor fieldas dangerous, since without any sensing information about such area weconsider it dangerous in order to increase the safety of navigation. Theconsequent road map is then built as depicted by graphic depiction 700of FIG. 7, illustrating 7 distinct cells. We can also choose to considerthe sensor field boundary safe, for example in the case where we havesome preliminary information on the boundary, e.g., the sensor field isindoor environment safely surrounded by walls or fences or the like. Inthis case, the road map is built as shown by graphic depiction 800 ofFIG. 8. Since the two cases are essentially similar, without loss ofgenerality, in the following, we mainly focus on the first case.

To describe the above in consistent terms, in one or more aspect, roadmap 114 can include multiple danger regions 142 (as well as,potentially, boundaries of road map 114) and mapping component 110 candivide road map 114 into multiple cells (e.g., C₁ . . . ) with each cellincluding exactly one danger region 142 and at least one exit point 152that represents a boundary along route backbone 132 between at least twoadjacent cells or a final destination for an evacuating entity 162.

With reference to FIG. 9, graphic depiction 900 provides a routebackbone and assigns directions to segments of the route backbone.Appreciably, at this point it is readily apparent that the road mapframework can be utilized as a backbone for navigating different usersinside the field. Exploring a route from the internal entity (e.g.,entity 160, 162) to the exits can therefore include: (1) connecting theexits and internal entity to the road backbone, respectively; (2)assigning directions on the road map; (3) navigating each user to thedestination exit.

For the sake of simplicity, assume there is only one exit point 152,even though it should be appreciated that numerous exit points couldexist. In order to build a route connecting the exit and the road mapbackbone, we find the exit in the cells. The route extends from the exitat each point along the most descending direction of the virtual fielduntil it reaches the border of the cell, e.g., the road backbone. In thediscrete sensor network, the most descending direction is to selectamong all its direct neighbors the one which has the least potentialvalue s.potential for a node. The route connecting the destination exitintersects the road backbone at a point we call the gateway (e.g.,gateway 170, 172). Building a route connecting the internal entity andthe road map backbone is a similar process that the route extends fromthe internal entities.

Directions for the road map (characterized by graphic depiction 900 asarrows) can indicate a safe path towards the gateway for each point onthe backbone. Thus, it is prudent to choose a path maximizing theclosest distance to the dangerous areas. Such can be achieved byflooding from the gateway throughout the road backbone. As introducedabove, the flooded message F (not shown) contains two items, d_(c),which records the minimum number of hops to the dangerous areas alongthe road from the current node to the gateway, and d_(r), which recordsthe number of hops along the road from the current node to the gateway.The basic idea is to choose a path with a minimum d_(c), and withshortest d_(r) while several paths have the same minimum d_(c). Eachpoint receives the flooded information from different directions.Usually, the flooded information only comes from the two directionsalong the road but possibly multiple directions at the branch pointswhere multiple roads segments intersect. A suitable programmatic exampleof this process is detailed in connection with Algorithm 1, listedbelow.

Algorithm 1 Direction Assigning Description: Phase 1 —Initialization  For each sensor node on the road backbone    s.nextHop ← null   s.rDist ← 0  End For Phase 2 —Flooding   m.d_(c)←s.mDist of Gatewaynode g   m.d_(r) ← 0  g broadcasts m throughout the road backbone Function w.Receive(Message m, FromNode v)   If (s.rDist < m.d_(c) )   s.nextHop ← v.ID    s.rDist ← m.d_(c)    w.tempDist ← m.d_(r)    m.d_(r) ← m.d_(r) + 1     m.d_(c) ← min (d_(c), s.mDist)   broadcast m   End If   Else     If ( s.rDist = m.d_(c) & w.tempDist <m.d_(r) )      s.nextHop ← v.ID       w.tempDist ← m.d_(r)       m.d_(r)← m.d_(r) + 1       m.d_(c) ← min (d_(c), s.mDist)      broadcast m   End If    End Else   Else discards m   End Else

In addition, graphic depiction 900 also illustrates that navigating eachentity to the destination exit includes three stages: (1) Each entity isguided from the inside of the cell to the road backbone. (2) Along theroad backbone, entities from different cells are navigated towards thegateway. (3) The “last-mile” navigation is guided along the route thatconnects the exit and the gateway on the road map.

Turning now to FIG. 10, computer implemented system 1000 that providesadditional features in connection with determining safety-orientednavigation paths through dangerous environments is depicted. Generally,system 1000 can include substantially any suitable feature or aspectdiscussed in connection with FIG. 1 or elsewhere herein. For example,system 1000 can include monitor component 102 that can receive hazardsignal 104 from an alarming sensor 106 as substantially detailed supra.In addition, system 1000 can also include mapping component 110 that canconstruct road map 114, also previously detailed in connection withsystem 100.

Additionally or alternatively, system 1000 can further include one ormore additional components such as navigation component 1002, updatecomponent 1008, and/or shortcut component 114. In more detail,navigation component 1002 that can configure a set of instructions 1004to guide mobile entity 1006 along at least a portion of recommended path130 to at least one safe area 150.

On the other hand, update component 1008 can be configured tocontinuously monitor data received from sensor array 120. Based uponsuch monitoring, update component 1008 can facilitate at least one realtime update 1010 to road map 114 upon detection of variation 1012 forone or more danger area 150 in the local environment 112, which in turncan correspond to one or more danger region 152 in the road map 114.

It should be understood that in one or more aspect, update component1008 can categorize variation 1010 as one of (1) an expanding variationidentified based upon an indication of a nominal sensor 108 that isadjacent to an alarming sensor 106 transitioning to from nominal mode toalarming mode, (2) a shrinking variation identified based upon anindication of an alarming sensor 106 that is adjacent to at least oneother alarming sensor 106 transitioning from alarming mode to shrinkingmode, (3) an emerging variation identified based upon an indication of anominal sensor that is adjacent to no alarming sensors transitioningfrom nominal mode to alarming mode, or (4) a diminishing variationidentified based upon an indication of an alarming sensor that isadjacent to no other alarming sensors transitioning from alarming modeto nominal mode.

In accordance therewith, update component 1008 can include in road map114 an expanding node in connection with the expanding variation andincreases dimensions of an adjacent danger region 142 to include theexpanding node. Additionally or alternatively, update component 1008 caninclude in the road map a shrinking node in connection with theshrinking variation and decreases dimension of an adjacent danger regionto exclude the shrinking node. Similarly, update component 1008 caninclude in the road map an emerging node in connection with the emergingvariation and add a new danger region to the road map. Likewise, updatecomponent 1008 can include in the road map a diminishing node inconnection with the diminishing variation and removes an associateddanger region from the road map 114.

While the above relates to dynamically redrawing danger regions 142, itshould be understood that update component 1008 can also redraw routebackbone 132 based upon these changes. For example, update component1008 can modify a d_(c) value only for nodes that are nearer to theemerging node or the expanding node than to any other node extant in adanger region 142. As another example, update component 1008 can modifya d_(c) value only for nodes that are nearer to the shrinking node orthe diminishing node than to any other node extant in a danger region142, wherein a modification to a d_(c) value facilitates re-constructionof the route backbone 132.

In more detail, when reacting to emergency dynamics (e.g., expanding,emerging, shrinking or diminishing danger regions 142), it is readilyapparent that for safety of evacuating entity, such changes should bereflected in the route backbone 132. Moreover, due to the emergencydynamics, the dangerous areas might vary during the navigation process,so it is prudent to allow for such changes rapidly. There are severalbasic types of variation of dangerous areas which include emerging,expanding, shrinking, and diminishing. In RMB, the variation ofdangerous areas is considered as a continuous process of switching aseries of points into or out of the dangerous areas. The expanding of adangerous area corresponds to a point beside the dangerous area isswitched into the dangerous area. The shrinking of a dangerous areacorresponds to a point on the boundary of the dangerous area is switchedout of the dangerous area. The emerging of a dangerous area correspondsto a point inside the safe district is switched into a dangerous area.The diminishing of a dangerous area corresponds to the last point of thedangerous area is switched to be safe

The updating principle additively rebuilds the road backbone accordingto the variations of dangerous areas. Each point in the field maintainsa status recording the set of the closest dangerous points to it and thedistance between them. Each time a point is switched into a dangerousarea, we only update those points which will take it as their closestdangerous point. Similarly, each time a point is switched out of adangerous area, we only update those points which record it as theirpreviously closest dangerous point. Each time a sensor node is switchedinto or out of the dangerous area, it generates a report and floods itwithin those nodes that record it in their s.mSet. Those nodesaccordingly update their s.mDist and s.mSet. The potential values ofs.potential for those nodes are also updated. The road map backbone isthen updated, and corresponding nodes update their s.road. The gatewaynode reinitiates a flood within the road backbone to reassign the pathdirections

Continuing with the discussion of FIG. 10, system 1000 can furtherinclude shortcut component 1014 that can identify one or more shortcutpath 1016 between two inscribed points extant on the route backbone. Theinscribed points, as well as other features associated with optimizingpath distance are further detailed infra in connection with FIGS. 11 and12. However, briefly, shortcut path 1016 can differ from the pathdescribed by route backbone 132. Particularly, shortcut path 1016 canrepresent a shortest distance between the two inscribed points whilemaintaining a minimum distance from a nearest danger region 142.

Shortcut component 1014 can further facilitate inclusion of the one ormore shortcut path 1016 to road map 114, which can be potentially beincluded in instructions 1004 delivered to mobile entity 1006. It shouldbe appreciated that the existence of a shortcut vis-à-vis route backbone132 is not necessarily guaranteed to result. Rather, shortcuts aretypically the result of the inclusion of multiple danger regions 142.Accordingly, shortcut component 1014 can initiate identification of theone or more shortcut path 1016 when road map 114 is divided intomultiple cells.

Moreover, upon identification of the one or more shortcut path 1016,shortcut component 1014 can establish a direction, D, for the one ormore shortcut path 1016 consistent with an associated route backboneportion direction. Such can be initiated upon inclusion of the one ormore shortcut path to the road map or upon an event signaled when anevacuating entity encounters one of the two inscribed points.

Turning now simultaneously to FIGS. 11 and 12, graphic depiction 1100illustrates construction of inscribed points for identifying shortcutsover route backbone, while graphic depiction 1200 illustratesidentification and/or construction of shortcuts.

As noted above, given the time factor can be significant in thenavigation process, in order to reduce excessively long routes, wemodify the road backbone as follows. Let the inscribed pointsP={p_(ij)|p_(ij) is the point on the road backbone between neighboringcells C_(i) and C_(j) that has the shortest distance d_(ij) to thedangerous areas D_(i) and D_(j), 1≦i,j≦n}, as illustrated by graphicdepiction 1100. Accordingly, in each cell we build a shortcut betweeneach pair of neighboring inscribed points. The shortcut is a shortestpath connecting two inscribed points that is no closer to the dangerousarea than the closest end. It is built through a constraint floodingwithin the area of points farther to the dangerous area than the twoinscribed points, as shown in graphic depiction 1200. These shortcutsare used as supplements for the original roads.

A direction can be assigned to the shortcut if there is a directionalpath between its two ends on the original road map backbone and theassigned direction is the same with the original direction. For thoseshortcuts without directional paths between their two ends on theoriginal road map backbone, we simply do not assign any direction forthem. Later when the users are navigated along the road map backbone,they will move along those shortcuts with directions if they encounterany.

When there are two or more exits in the field, we can further improvethe route safety and efficiency by navigating the users to relativelysafer and closer exit. In this case, each exit connects it to the roadbackbone and floods their gateway information along the backbone. Eachpoint on the backbone selects its direction heading towards the routewith the minimum distance to the dangerous areas. Among the routes ofthe same distance to the dangerous areas, it chooses the shortest one.The resulted directional road is multiple trees rooted at different exitgateways. Again, we can supplement the road map with shortcuts toimprove the route efficiency.

With the foregoing in mind, the following propositions in connectionwith RMB should be readily apparent:

First, the local minimum points of the virtual power field in each cellonly reside on the medial axis. This guarantees that we can successfullybuild a route connecting the exit and the road backbone without haltedat an intermediate point of local minimum. Such a route ensures that anypoint on the route is not closer to the dangerous area than thedestination exit.

Second, on the road backbone, from any point to the gateway, the pathalong the assigned directions maximizes the minimum distance to thedangerous areas.

Third, the selected navigation route maximizes the minimum distance ofall possible routes to the dangerous areas. This shows that the selectedroute provides user guaranteed safety in global span. Each user alongthe selected route never moves unnecessarily close to the dangerousareas. Meanwhile, the safety is globally guaranteed in the sense that wecannot find another route which is more distant away from the dangerousareas.

Fourth, for any given path segment on the selected navigation route, anysubstitute path will not be farther to the dangerous areas. Thisguarantees that any intermediate local path segment on the selectedroute yields the largest distance to the dangerous areas. We call thisproperty local safety. Local safety provides the user even strongersafety guarantee at each intermediate step such that at any local step,the selected route guides the user through the safest way.

Fifth, the impact of the emergency dynamics in the field is local. Whenthe dangerous area in a cell expands or shrinks continuously, only thepoints within that cell are affected. The emerging of a new dangerouspoint affects the points within the newly constructed cell and thediminishing of a dangerous point affects the points within the originalcell. In short, any emergency dynamic affects only a local districtbounded within the cell of the dangerous area. All points outside thisdistrict maintain their original status.

Sixth, after expanding or shrinking one point on A, the averagesector-like region affected is of size O(s′/√{square root over (s)}),assuming the sizes of a dangerous area A and its surrounding cell c ares and s′ respectively.

Seventh, the amortized size of the sector-like region affected by thevariation of dangerous areas is O(√{square root over (n)}). In eachupdating process when emergency varies, our method rebuilds the shape ofthe new road map with the cost of flooding and updating a local districtof an amortized size O(√{square root over (n)}). After rebuilding theshape of the new road map, we accordingly reassign the directions alongthe road backbone, which incurs local overhead on the compact backbone.

Eighth, the navigation route explored from the modified road map is aMax-Min route in terms of the distance to the dangerous areas.

FIGS. 13-15 illustrate various methodologies in accordance with one ormore embodiments described herein. While, for purposes of simplicity ofexplanation, the methodologies are shown and described as a series ofacts, it is to be understood and appreciated that the embodiments arenot limited by the order of acts, as some acts may occur in differentorders and/or concurrently with other acts from that shown and describedherein. For example, those skilled in the art will understand andappreciate that a methodology could alternatively be represented as aseries of interrelated states or events, such as in a state diagram.Moreover, not all illustrated acts may be required to implement amethodology in accordance with the various embodiments. Additionally, itshould be further appreciated that the methodologies disclosedhereinafter and throughout this specification are capable of beingstored on an article of manufacture to facilitate transporting andtransferring such methodologies to computers. The term article ofmanufacture, as used herein, is intended to encompass a computer programaccessible from any computer-readable device, carrier, or media.

With reference now to FIG. 13, exemplary computer implemented method1300 for facilitating safety-based navigational guidance through adangerous area is provided. Generally, at reference numeral 1302, a roadmap can be generated to represent a model of a local environment.

Moreover, at reference numeral 1304, at reference numeral 1304, nodes ofthe road map can be assigned to correspond to respective locationswithin the local environment of a set of networked sensors whose sensordetection radii define boundaries for the local environment. Hence, foreach sensor that appears in the local environment a corresponding nodecan be implemented in the road map. These nodes can serve as waypointswhen constructing safe paths. Moreover, additional nodes can be added tothe road map even when no corresponding sensor exists, which is detailedherein.

At reference numeral 1306, a notification from at least one alarmingsensor indicating a presence of danger in an area surrounding the atleast one alarming sensor can be received. For example, the notificationcan be electronically received by suitable hardware such as s receiveror transceiver.

Accordingly, at reference numeral 1308, at least one safe path fornavigating the local environment based upon a distance of nominalsensors from the at least one alarming sensor can be determined. Thesecalculations can be employed for construction of a safe route throughthe local environment. At reference numeral 1310, the at least one safepath in the road map can be represented as a route backbone thatintersects nodes that correspond to the nominal sensors included in theat least one safe path.

Referring to FIG. 14, exemplary computer implemented method 1400 forproviding addition features in connection with for facilitatingsafety-based navigational guidance through a dangerous area is depicted.At reference numeral 1402, at least one exit point corresponding to atarget destination for a mobile entity in the local environment can beincluded in the road map. Likewise, at reference numeral 1404, at leastone evacuation entity that corresponds to the mobile entity can beincluded in the road map. Similarly, at reference numeral 1406, agateway node extant on both the route backbone and a medial axis for theexit point can be included in the road map. Having fully constructed theroute backbone and attached the target location to the destinationlocation instructions for navigation can ensue.

However, to provide additional detail, it should be appreciated that,for example, at reference numeral 1408, the at least one safe path fornavigating the local environment can be determined further based upondistances from a nearest danger area and from the gateway node acquiredby the set of sensors by way of message flooding propagating tosuccessive sensors and origination from a sensor corresponding to thegateway node.

Moreover, at reference numeral 1410, a direction for at least onesegment of the route backbone can be determined based upon theinformation retained or propagated from the set of sensors. Thus, atreference numeral 1412, instructions for directing the evacuating entityto the exit point can be provided while maximizing a minimum distancefrom a danger area based upon the route backbone.

With reference now to FIG. 15, method 1500 for providing for updatingand/or optimizing with respect to a road map for traversing a dynamicenvironment is illustrated. At reference numeral 1502, a transitionnotification can be received from at one sensor in the set of sensorsindicating the at least one sensor has switched from a nominal mode toan alarming mode or switched from an alarming mode to a nominal mode.Accordingly, emergence dynamics, for example, and be detected andaccounted for.

For instance, at reference numeral 1504, the at least one sensor can becharacterized as one of an expanding node, a shrinking mode, an emergingnode, or a diminishing node based upon the transition notification andwhether any node adjacent to the at least one node corresponds to analarming sensor. Such characterization is described in more detailsupra. As a result of such characterization, at reference numeral 1506,dimensions of a danger region can be updated to include or exclude theat least one sensor, again, based upon the characterizing of referencenumeral 1504.

Moreover, at reference numeral 1508, nodes of the route backbone can beupdated by modifying distance data retained by corresponding sensors byway of message flooding only for sensors in which the at least onesensor newly represents a nearest danger region or was previouslydesignated as the nearest danger region.

At reference numeral 1510, the road map can be separated into distinctcells with each cell comprising a single danger region and at least oneexit point representing a boundary along the route backbone between atleast two adjacent cells or an original exit point.

In addition, at reference numeral 1512, at least one shortcut betweentwo inscribed points existing on the route backbone can be included inthe road map. It should be appreciated that the shortcut path differsfrom the route backbone and further represents a shortest distancebetween the two inscribed points while maintaining a minimum distancefrom a nearest danger region.

Referring now to FIG. 16, there is illustrated a block diagram of anexemplary computer system operable to execute the disclosedarchitecture. In order to provide additional context for various aspectsof embodiment(s) described herein, FIG. 16 and the following discussionare intended to provide a brief, general description of a suitablecomputing environment 1600 in which the various aspects of can beimplemented. Additionally, while one or more embodiments described abovemay be suitable for application in the general context ofcomputer-executable instructions that may run on one or more computers,those skilled in the art will recognize that such embodiments also canbe implemented in combination with other program modules and/or as acombination of hardware and software.

Generally, program modules include routines, programs, components, datastructures, etc., that perform particular tasks or implement particularabstract data types. Moreover, those skilled in the art will appreciatethat the inventive methods can be practiced with other computer systemconfigurations, including single-processor or multiprocessor computersystems, minicomputers, mainframe computers, as well as personalcomputers, hand-held computing devices, microprocessor-based orprogrammable consumer electronics, and the like, each of which can beoperatively coupled to one or more associated devices.

The illustrated aspects of the various embodiments may also be practicedin distributed computing environments where certain tasks are performedby remote processing devices that are linked through a communicationsnetwork. In a distributed computing environment, program modules can belocated in both local and remote memory storage devices.

A computer typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby the computer and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer-readable media can comprise computer storage mediaand communication media. Computer storage media can include volatile andnonvolatile, removable and non-removable media implemented in any methodor technology for storage of information such as computer-readableinstructions, data structures, program modules or other data. Computerstorage media includes, but is not limited to, RAM, ROM, EEPROM, flashmemory or other memory technology, CD-ROM, digital versatile disk (DVD)or other optical disk storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to store the desired information and which canbe accessed by the computer.

Communication media typically embodies computer-readable instructions,data structures, program modules or other data in a modulated datasignal such as a carrier wave or other transport mechanism, and includesany information delivery media. The term “modulated data signal” means asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,and not limitation, communication media includes wired media such as awired network or direct-wired connection, and wireless media such asacoustic, RF, infrared and other wireless media. Combinations of the anyof the above should also be included within the scope ofcomputer-readable media.

With reference again to FIG. 16, the exemplary environment 1600 forimplementing various aspects includes a computer 1602, the computer 1602including a processing unit 1604, a system memory 1606 and a system bus1608. The system bus 1608 couples to system components including, butnot limited to, the system memory 1606 to the processing unit 1604. Theprocessing unit 1604 can be any of various commercially availableprocessors. Dual microprocessors and other multi-processor architecturesmay also be employed as the processing unit 1604.

The system bus 1608 can be any of several types of bus structure thatmay further interconnect to a memory bus (with or without a memorycontroller), a peripheral bus, and a local bus using any of a variety ofcommercially available bus architectures. The system memory 1606includes read-only memory (ROM) 1610 and random access memory (RAM)1612. A basic input/output system (BIOS) is stored in a non-volatilememory 1610 such as ROM, EPROM, EEPROM, which BIOS contains the basicroutines that help to transfer information between elements within thecomputer 1602, such as during start-up. The RAM 1612 can also include ahigh-speed RAM such as static RAM for caching data.

The computer 1602 further includes an internal hard disk drive (HDD)1614 (e.g., EIDE, SATA), which internal hard disk drive 1614 may also beconfigured for external use in a suitable chassis (not shown), amagnetic floppy disk drive (FDD) 1616, (e.g., to read from or write to aremovable diskette 1618) and an optical disk drive 1620, (e.g., readinga CD-ROM disk 1622 or, to read from or write to other high capacityoptical media such as the DVD). The hard disk drive 1614, magnetic diskdrive 1616 and optical disk drive 1620 can be connected to the systembus 1608 by a hard disk drive interface 1624, a magnetic disk driveinterface 1626 and an optical drive interface 1628, respectively. Theinterface 1624 for external drive implementations includes at least oneor both of Universal Serial Bus (USB) and IEEE1394 interfacetechnologies. Other external drive connection technologies are withincontemplation of the subject matter claimed herein.

The drives and their associated computer-readable media providenonvolatile storage of data, data structures, computer-executableinstructions, and so forth. For the computer 1602, the drives and mediaaccommodate the storage of any data in a suitable digital format.Although the description of computer-readable media above refers to aHDD, a removable magnetic diskette, and a removable optical media suchas a CD or DVD, it should be appreciated by those skilled in the artthat other types of media which are readable by a computer, such as zipdrives, magnetic cassettes, flash memory cards, cartridges, and thelike, may also be used in the exemplary operating environment, andfurther, that any such media may contain computer-executableinstructions for performing the methods of the various embodiments.

A number of program modules can be stored in the drives and RAM 1612,including an operating system 1630, one or more application programs1632, other program modules 1634 and program data 1636. All or portionsof the operating system, applications, modules, and/or data can also becached in the RAM 1612. It is appreciated that the various embodimentscan be implemented with various commercially available operating systemsor combinations of operating systems.

A user can enter commands and information into the computer 1602 throughone or more wired/wireless input devices, e.g., a keyboard 1638 and apointing device, such as a mouse 1640. Other input devices 1641 mayinclude a speaker, a microphone, a camera or another imaging device, anIR remote control, a joystick, a game pad, a stylus pen, touch screen,or the like. These and other input devices are often connected to theprocessing unit 1604 through an input-output device interface 1642 thatcan be coupled to the system bus 1608, but can be connected by otherinterfaces, such as a parallel port, an IEEE1394 serial port, a gameport, a USB port, an IR interface, etc.

A monitor 1644 or other type of display device is also connected to thesystem bus 1608 via an interface, such as a video adapter 1646. Inaddition to the monitor 1644, a computer typically includes otherperipheral output devices (not shown), such as speakers, printers, etc.

The computer 1602 may operate in a networked environment using logicalconnections via wired and/or wireless communications to one or moreremote computers, such as a remote computer(s) 1648. The remotecomputer(s) 1648 can be a workstation, a server computer, a router, apersonal computer, a mobile device, portable computer,microprocessor-based entertainment appliance, a peer device or othercommon network node, and typically includes many or all of the elementsdescribed relative to the computer 1602, although, for purposes ofbrevity, only a memory/storage device 1650 is illustrated. The logicalconnections depicted include wired/wireless connectivity to a local areanetwork (LAN) 1652 and/or larger networks, e.g., a wide area network(WAN) 1654. Such LAN and WAN networking environments are commonplace inoffices and companies, and facilitate enterprise-wide computer networks,such as intranets, all of which may connect to a global communicationsnetwork, e.g., the Internet.

When used in a LAN networking environment, the computer 1602 isconnected to the local network 1652 through a wired and/or wirelesscommunication network interface or adapter 1656. The adapter 1656 mayfacilitate wired or wireless communication to the LAN 1652, which mayalso include a wireless access point disposed thereon for communicatingwith the wireless adapter 1656.

When used in a WAN networking environment, the computer 1602 can includea modem 1658, or is connected to a communications server on the WAN1654, or has other means for establishing communications over the WAN1654, such as by way of the Internet. The modem 1658, which can beinternal or external and a wired or wireless device, is connected to thesystem bus 1608 via the interface 1642. In a networked environment,program modules depicted relative to the computer 1602, or portionsthereof, can be stored in the remote memory/storage device 1650. It willbe appreciated that the network connections shown are exemplary andother means of establishing a communications link between the computerscan be used.

The computer 1602 is operable to communicate with any wireless devicesor entities operatively disposed in wireless communication, e.g., aprinter, scanner, desktop and/or portable computer, portable dataassistant, communications satellite, any piece of equipment or locationassociated with a wirelessly detectable tag (e.g., a kiosk, news stand,restroom), and telephone. This includes at least Wi-Fi and Bluetooth™wireless technologies. Thus, the communication can be a predefinedstructure as with a conventional network or simply an ad hoccommunication between at least two devices.

Wi-Fi, or Wireless Fidelity, allows connection to the Internet from acouch at home, a bed in a hotel room, or a conference room at work,without wires. Wi-Fi is a wireless technology similar to that used in acell phone that enables such devices, e.g., computers, to send andreceive data indoors and out; anywhere within the range of a basestation. Wi-Fi networks use radio technologies called IEEE802.11 (a, b,g, etc.) to provide secure, reliable, fast wireless connectivity. AWi-Fi network can be used to connect computers to each other, to theInternet, and to wired networks (which use IEEE802.3 or Ethernet). Wi-Finetworks operate in the unlicensed 2.4 and 5 GHz radio bands, at an 16Mbps (802.11b) or 54 Mbps (802.11a) data rate, for example, or withproducts that contain both bands (dual band), so the networks canprovide real-world performance similar to the basic “10BaseT” wiredEthernet networks used in many offices.

Referring now to FIG. 17, there is illustrated a schematic block diagramof an exemplary computer compilation system operable to execute thedisclosed architecture. The system 1700 includes one or more client(s)1702. The client(s) 1702 can be hardware and/or software (e.g., threads,processes, computing devices). The client(s) 1702 can house cookie(s)and/or associated contextual information by employing one or moreembodiments described herein, for example.

The system 1700 also includes one or more server(s) 1704. The server(s)1704 can also be hardware and/or software (e.g., threads, processes,computing devices). The servers 1704 can house threads to performtransformations by employing one or more embodiments, for example. Onepossible communication between a client 1702 and a server 1704 can be inthe form of a data packet adapted to be transmitted between two or morecomputer processes. The data packet may include a cookie and/orassociated contextual information, for example. The system 1700 includesa communication framework 1706 (e.g., a global communication networksuch as the Internet) that can be employed to facilitate communicationsbetween the client(s) 1702 and the server(s) 1704.

Communications can be facilitated via a wired (including optical fiber)and/or wireless technology. The client(s) 1702 are operatively connectedto one or more client data store(s) 1708 that can be employed to storeinformation local to the client(s) 1702 (e.g., cookie(s) and/orassociated contextual information). Similarly, the server(s) 1704 areoperatively connected to one or more server data store(s) 1710 that canbe employed to store information local to the servers 1704.

What has been described above includes examples of the variousembodiments. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the embodiments, but one of ordinary skill in the art mayrecognize that many further combinations and permutations are possible.Accordingly, the detailed description is intended to embrace all suchalterations, modifications, and variations that fall within the spiritand scope of the appended claims.

In particular and in regard to the various functions performed by theabove described components, devices, circuits, systems and the like, theterms (including a reference to a “means”) used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., a functional equivalent), even though not structurallyequivalent to the disclosed structure, which performs the function inthe herein illustrated exemplary aspects of the embodiments. In thisregard, it will also be recognized that the embodiments includes asystem as well as a computer-readable medium having computer-executableinstructions for performing the acts and/or events of the variousmethods.

In addition, while a particular feature may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.Furthermore, to the extent that the terms “includes,” and “including”and variants thereof are used in either the detailed description or theclaims, these terms are intended to be inclusive in a manner similar tothe term “comprising.”

What is claimed is:
 1. A computer implemented system that determinessafety-oriented navigation paths, comprising: a monitor componentconfigured to receive a hazard signal from at least one alarming sensorincluded in a sensor array distributed in a local environment bounded bya detection radius of the sensor array, wherein the hazard signalindicates a detected presence of danger proximal to the at least onealarming sensor, and wherein a sensor from the sensor array is notrequired to maintain location information relating to a location withinthe local environment; and a mapping component configured to construct aroad map scaled to dimensions of the local environment, wherein the roadmap includes a route backbone that depicts one or more recommended pathsthrough the local environment selected based on a distance thatsatisfies a defined condition with respect to reduction of distance fromthe detected presence of danger.
 2. The system of claim 1, wherein theroute backbone comprises a set of edges that join a sequence of adjacentnodes that correspond to respective locations within the localenvironment of nominal sensors included in the sensor array.
 3. Thesystem of claim 1, wherein at least one of: the mapping componentfurther identifies at least one safe area within the local environmentand plots an exit point on the road map that corresponds with the atleast one safe area; the mapping component further identifies at leastone mobile entity extant in the local environment and plots at least oneevacuating entity that corresponds to the at least one mobile entity onthe road map connected to a proximal point of the route backbone; or themapping component connects at least one exit point to the route backbonewith an edge that intersects a proximal point, denoted a gateway, on theroute backbone and depicts a recommended path through the localenvironment.
 4. The system of claim 3, wherein the mapping componentconnects the at least one exit point to the gateway of the routebackbone based upon a concatenation of a medial axis of the exit point.5. The system of claim 4, wherein the medial axis includes a set ofpoints, wherein a point from the set of points is a minimum distancefrom at least two danger regions.
 6. The system of claim 1, wherein themapping component includes in the road map at least one danger regionthat encompasses a contiguous set of alarming sensors and thatcorresponds to a danger area in the local environment.
 7. The system ofclaim 6, wherein the mapping component treats regions beyond the localenvironment that correspond to areas outside the detection radius of thesensor array as one or more of the at least one danger region or themapping component treats at least one region beyond the localenvironment that corresponds to areas outside the detection radius ofthe sensor array as a safe region and plots an exit point to correspondto the safe region.
 8. The system of claim 1, wherein the mappingcomponent assigns a potential value to a node included in the road mapbased at least in part upon data received from a corresponding sensor,wherein the potential value is inversely proportional to a distancebetween the corresponding sensor and a nearest danger area.
 9. Thesystem of claim 8, wherein at least one of: the mapping componentmaximizes a minimum distance from all or a portion of danger regionsincluded in the road map to construct the route backbone and furtherassigns a direction to one or more segment of the route backbone basedupon descending potential values for nodes included in the one or moresegment; the mapping component connects an exit point or an evacuationentity to the route backbone based upon descending potential values forconnected nodes extending from the exit point or the evacuation entityto the route backbone; or the potential value of the node is determinedbased at least in part upon information that propagates from a gatewaysensor that corresponds to a gateway for the road map.
 10. The system ofclaim 9, wherein information propagates from the gateway sensor to othersensors in the sensor array that correspond to nodes included in theroad map, wherein the information includes an indication of distance toa nearest danger area, denoted d_(c), an indication of a distance to thegateway sensor that increases as the information propagates tosubsequent other sensors, denoted d_(r), and a direction for the routebackbone for nodes along the route backbone, denoted D.
 11. The systemof claim 10, wherein the mapping component constructs the route backbonebased upon a comparison between multiple nodes included in the road map,wherein the comparison selects nodes associated with a larger d_(c), ora smaller d_(r) when d_(c) are equal for compared nodes.
 12. The systemof claim 1, wherein the road map includes multiple danger regions andthe mapping component divides the road map into multiple cells with eachcell including exactly one danger region and at least one exit pointthat represents a boundary along the route backbone between at least twoadjacent cells or a final destination for an evacuating entity.
 13. Thesystem of claim 1, further comprising a navigation component thatconfigures a set of instructions to guide the mobile entity along atleast a portion of the recommended path to at least one safe area. 14.The system of claim 1, further comprising an update component configuredto continuously monitor data received from the sensor array and thatfacilitates at least one real time update to the road map upon detectionof a variation of one or more danger area in the local environment thatcorresponds to one or more danger region in the road map.
 15. The systemof claim 14, wherein at least one of: the update component categorizesthe variation as one of (1) an expanding variation identified based uponan indication of a nominal sensor that is adjacent to an alarming sensortransitioning from nominal mode to alarming mode, (2) a shrinkingvariation identified based upon an indication of an alarming sensor thatis adjacent to at least one other alarming sensor transitioning fromalarming mode to nominal mode, (3) an emerging variation identifiedbased upon an indication of a nominal sensor that is adjacent to noalarming sensors transitioning from nominal mode to alarming mode, or(4) a diminishing variation identified based upon an indication of analarming sensor that is adjacent to no other alarming sensorstransitioning from alarming mode to nominal mode; the update componentincludes in the road map an expanding node in connection with theexpanding variation and increases dimensions of an adjacent dangerregion to include the expanding node; includes in the road map ashrinking node in connection with the shrinking variation and decreasesdimension of an adjacent danger region to exclude the shrinking node;includes in the road map an emerging node in connection with theemerging variation and adds a new danger region to the road map; orincludes in the road map a diminishing node in connection with thediminishing variation and removes an associated danger region from theroad map; or the update component modifies a d_(c) value only for nodesthat are nearer to the emerging node or the expanding node than to anyother node extant in a danger region, or the update component modifies ad_(c) value only for nodes that are nearer to the shrinking node or thediminishing node than to any other node extant in a danger region,wherein a modification to a d_(c) value facilitates re-construction ofthe route backbone.
 16. The system of claim 1, further comprising ashortcut component that identifies one or more shortcut path between twoinscribed points extant on the route backbone, wherein the shortcut pathdiffers from the route backbone and represents a shortest distancebetween the two inscribed points while maintaining a minimum distancefrom a nearest danger region, and wherein at least one of: the shortcutcomponent facilitates inclusion of the one or more shortcut path to theroad map; the shortcut component initiates identification of the one ormore shortcut path when the road map is divided into multiple cells; orthe shortcut component establishes a direction for the one or moreshortcut path consistent with an associated route backbone portiondirection upon inclusion of the one or more shortcut path to the roadmap or upon an event signaled when an evacuating entity encounters oneof the two inscribed points.